Automatic transmission

Abstract

An automatic transmission includes the transmission control device which sets a control time upon changeover from the second gear condition to the third gear condition during which the brake device is maintained in the engaged condition until changing to the disengaged condition. The transmission control device also adds a compensating time to the control time upon changeover from the second gear condition to the third gear condition in certain circumstances such as when changeover from the second gear condition to the third gear condition follows operation under the first gear condition, and when change over from the second gear condition to the third gear condition follows vehicle operation under the second gear condition for a period exceeding a predetermined time (e.g., 10 seconds).

What is claimed is: 
     
       1. An automatic transmission comprising: a housing;   a planetary gear device disposed in the housing and including a ring gear, a sun gear which is disposed inside of the ring gear and which is rotated around an axis that is coaxial with the ring gear, a carrier, and a pinion which is rotatably supported on the carrier and which is engageable with the ring gear and the sun gear, the sun gear being provided with a pressure chamber for receiving oil;   an input side shaft which rotates with the ring gear;   an output side shaft which rotates with the carrier;   a clutch device selectively positionable in an engaged condition in which the sun gear is engaged with the input side shaft and a disengaged condition in which the sun gear is disengaged from the input side shaft in response to oil pressure in the pressure chamber of the sun gear;   a check valve which permits oil in the pressure chamber to flow outside of the pressure chamber when the oil pressure in the pressure chamber is lower than a predetermined value and which prevents oil in the pressure chamber from flowing outside of the pressure chamber when the oil pressure in the pressure chamber is higher than the predetermined value;   a brake device selectively positionable in an engaged condition in which the sun gear is engaged with the housing and a disengaged condition in which the sun gear is disengaged from the housing; and   transmission control means for controlling operation of the clutch device and the brake device to changeover among a first operating condition in which the clutch device and the brake device are in the disengaged condition, a second operating condition in which the clutch device is in the disengaged condition and the brake device is in the engaged condition, and a third operating condition in which the clutch device is in the engaged condition and the brake device is in the disengaged condition, the transmission control means including means for setting a control time upon changeover from the second operating condition to the third operating condition during which the brake device is maintained in the engaged condition until changing to the disengaged condition, and compensating means for adding a compensating time to the control time upon changeover from the second operating condition to the third operating condition at least when changeover from the second operating condition to the third operating condition follows operation under the first operating condition, said compensating time being determined on the basis of the time until the oil pressure in the pressure chamber becomes a predetermined value after oil is supplied to an empty pressure chamber.   
     
     
       2. An automatic transmission as recited in claim 1, wherein the compensating time is a time required to increase the oil pressure in the pressure chamber to a predetermined value. 
     
     
       3. An automatic transmission as recited in claim 2, wherein the control time is determined in accordance with an opening degree of a throttle valve. 
     
     
       4. An automatic transmission as recited in claim 3, wherein the compensating time is determined in accordance with the opening degree of the throttle valve. 
     
     
       5. An automatic transmission as recited in claim 1, wherein the compensating means adds the compensating time to the control time upon changeover from the second operating condition to the third operating condition when changeover from the second operating condition to the third operating condition follows operation under the second operating condition that has continued longer than a predetermined time. 
     
     
       6. An automatic transmission as recited in claim 5, wherein the predetermined time is determined based on the time required for the oil pressure in the pressure chamber to drop to a predetermined pressure after changeover to the second operating condition. 
     
     
       7. An automatic transmission as recited in claim 1, wherein the control time is determined in accordance with an opening degree of a throttle valve. 
     
     
       8. An automatic transmission as recited in claim 7, wherein the compensating time is determined in accordance with the opening degree of the throttle valve. 
     
     
       9. An automatic transmission comprising: a housing;   a planetary gear device disposed in the housing and including a ring gear, a sun gear which is disposed inside of the ring gear and which is rotated around an axis that is coaxial with the ring gear, a carrier, and a pinion which is rotatably supported on the carrier and which is engageable with the ring gear and the sun gear, the sun gear being provided with a pressure chamber for receiving oil;   an input side shaft which rotates with the ring gear;   an output side shaft which rotates with the carrier;   a clutch device selectively positionable in an engaged condition in which the sun gear is engaged with the input side shaft and a disengaged condition in which the sun gear is disengaged from the input side shaft in response to oil pressure in the pressure chamber of the sun gear;   a check valve which permits oil in the pressure chamber to flow outside of the pressure chamber when the oil pressure in the pressure chamber is lower than a predetermined value and which prevents oil in the pressure chamber from flowing outside of the pressure chamber when the oil pressure in the pressure chamber is higher than the predetermined value;   a brake device selectively positionable in an engaged condition in which the sun gear is engaged with the housing and a disengaged condition in which the sun gear is disengaged from the housing; and   transmission control means for controlling operation of the clutch device and the brake device to changeover among a first operating condition in which the clutch device and the brake device are in the disengaged condition, a second operating condition in which the clutch device is in the disengaged condition and the brake device is in the engaged condition, and a third operating condition in which the clutch device is in the engaged condition and the brake device is in the disengaged condition, the transmission control means including means for setting a control time upon changeover from the second operating condition to the third operating condition during which the brake device is maintained in the engaged condition until changing to the disengaged condition, the transmission control means including compensating means for adding a compensating time to the control time upon changeover from the second operating condition to the third operating condition when changeover from the second operating condition to the third operating condition follows operation under the second operating condition that has continued longer than a predetermined time.   
     
     
       10. An automatic transmission as recited in claim 9, wherein the predetermined time is determined based on the time required for the oil pressure in the pressure chamber to drop to a predetermined pressure after changeover to the second operating condition. 
     
     
       11. An automatic transmission comprising: a housing;   a planetary gear device disposed in the housing and including a ring gear, a sun gear which is disposed inside of the ring gear and which is rotated around an axis that is coaxial with the ring gear, a carrier, and a pinion which is rotatably supported on the carrier and which is engageable the ring gear and the sun gear, the sun gear being provided with a pressure chamber for receiving oil;   an input side shaft which rotates with the ring gear;   an output side shaft which rotates with the carrier;   a clutch device selectively positionable in an engaged condition in which the sun gear is engaged with the input side shaft and a disengaged condition in which the sun gear is disengaged from the input side shaft in response to oil pressure in the pressure chamber of the sun gear;   a check valve which permits oil in the pressure chamber to flow outside of the pressure chamber when the oil pressure in the pressure chamber is lower than a predetermined value and which prevents oil in the pressure chamber from flowing outside of the pressure chamber when the oil pressure in the pressure chamber is higher than the predetermined value;   a brake device selectively positionable in an engaged condition in which the sun gear is engaged with the housing and a disengaged condition in which the sun gear is disengaged from the housing; and   transmission control means for controlling operation of the clutch device and the brake device to effect a changeover operation among a plurality of operating conditions, the transmission control means including means for setting a control time upon changeover from one operating condition to another operating condition during which the brake device is maintained in the engaged condition until changing to the disengaged condition, and for adding a compensating time to the control time when the changeover operation from the one operating condition to the another operating condition is determined to be a changeover operation falling within a predetermined group of changeover operations.   
     
     
       12. An automatic transmission recited in claim 11, wherein the transmission control means controls operation of the clutch device and the brake device to changeover among a first operating condition in which the clutch device and the brake device are in the disengaged condition, a second operating condition in which the clutch device is in the disengaged condition and the brake device is in the engaged condition, and a third operating condition in which the clutch device is in the engaged condition and the brake device is in the disengaged condition, wherein said predetermined group of changeover operations includes a changeover operation from the second operating condition to the third operating condition following operation under the second operating condition that has continued longer than a predetermined time. 
     
     
       13. An automatic transmission recited in claim 11, wherein the transmission control means controls operation of the clutch device and the brake device to changeover among a first operating condition in which the clutch device and the brake device are in the disengaged condition, a second operating condition in which the clutch device is in the disengaged condition and the brake device is in the engaged condition, and a third operating condition in which the clutch device is in the engaged condition and the brake device is in the disengaged condition, wherein said predetermined group of changeover operations includes a changeover operation from the second operating condition to the third operating condition directly following operation under the first operating condition. 
     
     
       14. An automatic transmission recited in claim 11, including a map for determining the compensating time, said compensating time being determined based on a throttle opening degree.